The invention relates to a device for converting an electric signal into an acoustic signal, comprising an input terminal for receiving the electric signal, an amplifier unit having an input coupled to the input terminal, and an output, and an electrostatic transducer unit coupled to the output of the amplifier unit, the electrostatic transducer unit comprising N electrostatic transducers, N being larger than or equal to 2. Such a device is known from German Offenlegungsschrift No. 1,762,375.
Electrostatic loudspeakers are known in a construction of a first type comprising, a diaphragm in the form of a foil on which an electrode is arranged, and a stationary second electrode which is spaced from the diaphragm.
A construction of a second type is the push-pull loudspeaker. This construction employs two stationary electrodes arranged at a specific distance on opposite sides of the diaphragm. The electrode arranged on the diaphragm may be a vacuum-deposited conductor layer of, for example, aluminum However, it is alternatively possible to provide an electrode in the form of a high-impedance layer on the diaphragm, so that less distortion is produced than in the case of a low-impedance layer, see German patent specification No. 1,088,546.
For a high sensitivity of the loudspeaker the diaphragm and the stationary electrode(s) must be arranged at a small distance from each other. However, the surface area of the diaphragm is then required to be large in order to achieve an adequate low-frequency acoustic radiation of the loudspeaker When the loudspeaker has a large radiation surface this gives rise to the problem of acoustic waves radiated at higher frequencies being concentrated.
This may be solved by reducing the dimensions of the effective radiation surface at increasing frequencies. This solution is known per se and is employed in a column comprising a plurality of loudspeakers arranged one above the other, see U.S. Pat. No. 4,233,472.